On Wednesday, 13 March 2019 20:49:27 UTC, Mathew Newton wrote:

http://www.newtonnet.co.uk/permanent/celotex.jpg

The 100mm boards also have an ever so slight bow to them; not enough to cause me an issue but I wondered if the bowing and wrinkles were the result of differential shrinkage within the core?

Any cause for concern?

Thanks everyone for the comments. It seems the vast majority thought it was a non-issue. I heard back from Celotex Technical Support and they said:

'In regards to the facer issue occasionally the facer can have a crinkled appearance as a result of the manufacturing process but should be consider to be an aesthetic issue only. Whilst the visual appearance of these boards is not aesthetically pleasing they continue to be suitable. The thermal value and structural integrity of the boards is unaffected and they remain fit for their intended purpose as thermal insulation.'

The supplier said similar and they also offered to replace any bowed boards should they be a problem for my application but the bowing is only slight (10mm over the full length) and so I don't think that'll be necessary.